An ion source is a device that ionizes gas molecules. The ionized molecules are then accelerated and emitted in a beam towards a substrate. The ionized beam may be used for cleaning, activation, polishing, etching, and/or deposition of thin-film coatings/layer(s). Example ion sources are disclosed, for example, in U.S. Pat. Nos. 7,872,422; 7,488,951; 7,030,390; 6,988,463; 6,987,364; 6,815,690; 6,812,648; 6,359,388; and Re. 38,358; the disclosures of each of which are hereby incorporated herein by reference.
FIGS. 1-2 illustrate a conventional closed drift of the anode layer type ion source. FIG. 1 is a side cross-sectional view of an ion beam source with an ion beam emitting slit defined in the cathode. FIG. 2 is a corresponding sectional plan view along section line II-II of FIG. 1. FIG. 3 is a sectional plan view similar to FIG. 2 and illustrates that the ion beam emitting gap may be generally ovular as opposed to generally circular in nature.
Referring to FIGS. 1-3, the ion source includes a hollow housing made of a magnetoconductive material such as steel, which is used as a cathode 5. Cathode 5 includes cylindrical or oval side wall 7, a closed or partially closed bottom wall 9, and an approximately flat top wall 11 in which a circular or oval ion emitting slit and/or aperture (also sometimes referred to as a “discharge gap”) 15 is defined. Ion emitting slit/aperture 15 includes an inner periphery as well as an outer periphery. The portion of top cathode wall 5, 11 inside of the slit 15 may be considered the inner cathode, whereas the portion of the top cathode wall 5, 11 outside of the slit 15 may be considered the outer cathode. Deposit and/or maintenance gas supply aperture or hole(s) 21 is/are formed in bottom wall 9. A magnetic system including an array of magnets 23 with poles N and S of opposite polarity is placed inside the housing between bottom wall 9 and top wall 11. The purpose of the magnetic system with a closed magnetic circuit formed by the magnet 23 and cathodes 5 and 11, and is to induce a substantially transverse magnetic field (MF) in an area that is proximate to ion emitting slit 15.
The ion source may be entirely or partially within conductive wall 50, and/or wall 50 may at least partially define the deposition chamber. In certain instances, wall 50 may entirely surround the source and substrate 45, while in other instances the wall 50 may only partially surround the ion source and/or substrate.
A circular or oval shaped conductive anode 25, electrically connected to the positive pole of electric power source 29, is arranged so as to at least partially surround magnet 23 and be approximately concentric therewith. Anode 25 may be fixed inside the housing by way of insulating ring 31 (e.g., of ceramic). Anode 25 defines a central opening therein in which magnet 23 is located. The negative pole of electric power source 29 is connected to cathode 5 and may or may not be grounded, so that the cathode is negative with respect to the anode. Generally speaking, the anode 25 is generally biased positive by several thousand volts. Meanwhile, the cathode (the term “cathode” as used herein includes the inner and/or outer portions thereof) is generally held at ground potential. One example of a conventional ion source includes an anode having a flat top surface approximately 2 mm from the bottom of both the inner and outer cathodes.
The conventional ion beam source of FIGS. 1-3 is intended for the formation of a unilaterally directed tubular ion beam, flowing in the direction toward substrate 45. Substrate 45 may or may not be biased in different instances. The ion beam emitted from the area of slit/aperture 15 is in the form of a circle in the FIG. 2 embodiment and in the form of an oval (e.g., race-track) in the FIG. 3 embodiment. The conventional ion beam source of FIGS. 1-3 operates as follows in a depositing mode when it is desired that the ion beam deposit at least one layer on substrate 45. A vacuum chamber in which the substrate 45 and slit/aperture 15 are located is evacuated, and a depositing gas (e.g., a hydrocarbon gas such as acetylene, or the like) is fed into the interior of the source or in the background via aperture(s) 21 or in any other suitable manner. A maintenance gas (e.g., argon) may also be fed into the source in certain instances, along with or instead of the depositing gas. Power supply 29 is activated and an electric field is initially generated between anode 25 and cathode 5, which accelerates electrons to high energy. Anode 25 is positively biased by several thousand volts, and cathode 5 is at ground potential as shown in FIG. 1. Electron collisions with the gas in, and/or proximate to, aperture/slit 15 leads to ionization and a plasma is generated. “Plasma” herein means a cloud of gas including ions of a material to be accelerated toward substrate 45. The plasma expands and fills (or at least partially fills) a region including slit/aperture 15. An electric field is produced in slit 15, oriented in a direction that is substantially perpendicular to the transverse magnetic field, which causes the ions to propagate toward substrate 45. Electrons in the ion acceleration space in and/or proximate to slit/aperture 15 are propelled by the known E×B drift in a closed loop path within the region of crossed electric and magnetic field lines proximate to slit/aperture 15. These circulating electrons contribute to ionization of the gas (the term “gas” as used herein means at least one gas), so that the zone of ionizing collisions extends beyond the electrical gap between the anode and cathode and includes the region proximate to slit/aperture 15 on one and/or both sides of the cathode 5. For purposes of example, consider the situation where acetylene (C2H2) depositing gas is/are utilized by the ion source of FIGS. 1-3 in a depositing mode. The acetylene depositing gas passes through the gap between anode 25 and cathode 5.
The inventor of the instant application has recognized that it would be desirable to further improve upon conventional ion source designs.
For example, in certain instances, an ion source may have low dynamic deposition rates (DDR). This may be a consequence of designs that produce a high voltage/low current discharge operating regime (e.g., higher energy but fewer ions per unit of time).
As another example, when operating an ion source with carbon bearer precursors (e.g., for DLC film deposition), contamination may quickly build up on the different components of the ion source. This carbon debris accumulation combined with the source's geometry and stack up dimensions, and its high operating discharge voltages, may produce heavy arching and plasma instabilities which, in time, may cause the termination of the deposition process.
In certain instances, generation of high energy ions may be undesirable, for example in large area coating applications. In these instances, excessive energetic ion collisions may damage the integrity of the coating being deposited (e.g., when ion beam assisted deposition (IBAD) and/or post-deposition coating treatment is being used).
Thus, it will be appreciated that there is a need in the art for improved ion source devices and/or improved techniques of using ion source deposition.
In certain example embodiments, an exemplary ion source apparatus may be used for direct coating deposition (e.g., of diamond like carbon, etc.), substrate surface cleaning and activations, surface roughness alteration, ion beam assisted deposition for coating densification, dopant implantations, coating phase alteration, and/or the like.
In certain example embodiments, carbon based precursors, such as, for example, alkane, alkene, and/or alkyne inclusive gasses may be used. In certain example embodiments, a higher ion current density is achieved (e.g., more ions per unit of time).
In certain example embodiments, the discharge voltage may be relatively lower than that of conventional ion source devices. This may result in less energetic ions.
In certain example embodiments, the relationship between ion current density and depositions may results in higher ion beam current and higher process DDR.
In certain example embodiments, the construction of an ion source apparatus may reduce the carbon contamination build up incurred during the DLC deposition process.
In certain example embodiments, an ion beam source is provided that is configured to emit an ion beam in a direction of a substrate. The ion source includes a cathode that at least partially defines a discharge opening, the discharge opening having a predetermined width. An anode is located spaced apart from the cathode by a predetermined depth, the direction in which the ion beam is to be emitted being substantially parallel to a direction from the anode to the discharge opening in the cathode. First and second ceramic walls at least partially define a discharge channel between the anode and the cathode. At least one magnet is provided that is configured to generate a magnetic field in at least the discharge opening.
In certain example embodiments, a method of ion depositing a layer on a substrate is provided. An ion source is provided, with the ion source including: at least one cathode; an anode that is located proximate to an aperture defined in the cathode, the aperture having a predetermined width and a predetermined depth that separates the anode from the aperture; at least one magnet that generates a magnetic field proximate to the aperture defined in the cathodes; first and second ceramic barrier walls at least partially define a passage between the anode and the aperture in the cathode. Power is provided to the at least one magnet to generate the magnetic field. A gas is provided to an area proximate to the aperture defined in the cathode, the provided gas being ionized and emitted towards the substrate.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.